Electrochemical Promotion of Oxygen Reduction on Gold with Aluminum Phosphate Overlayer

The activities of Au electrodes with an AlPO4 overlayer were examined for oxygen-reduction reactions in alkaline media. Oxygen molecules on gold catalysts are mainly reduced by a two-electron path, forming hydrogen peroxide with half efficiency. On the AlPO4 overlayer deposited Au, larger current densities corresponding to a nearly four-electron path were recorded within the potential range of approximately 0.7−1.0 V, which were correlated with the decomposition (disproportionation) of hydrogen peroxide. This enhancement was attributed to the electronic interactions and changed activities of the intermediate state, as confirmed by X-ray photoelectron spectroscopy and the voltammetric profiles of hydrogen peroxide, respectively

Modification of Gold Catalysis with Aluminum Phosphate for Oxygen-Reduction Reaction

The activities of Au/AlPO4 nanocomposites with the variation of metal phosphates were examined for oxygen-reduction reactions, both in an alkaline and acidic environment. In an alkaline media, the activities of the Au/AlPO4 nanocomposites on the oxygen-reduction were enhanced. The steeper reduction slope as well as larger reduction current density were observed in the potential range of approximately 0.8−1.0 V (vs reversible hydrogen electrode) with the newly appeared peak at ∼0.85 V. In an acidic media, the oxygen reduction on the Au/AlPO4 nanocomposites presented both higher onset potential and steeper reduction slope than that on the Au catalyst. Such enhancements were attributed to the electronic interactions between Au and AlPO4, as confirmed by X-ray photoelectron spectroscopy

Electronic Effect in Methanol Dehydrogenation on Pt Surfaces: Potential Control during Methanol Electrooxidation

Establishing a relationship between the catalytic activity and electronic structure of a transition-metal surface is important in the prediction and design of a new catalyst in fuel cell technology. Herein, we introduce a novel approach for identifying the methanol oxidation reactions, especially focusing on the effect of the Pt electronic structure on methanol dehydrogenation. By systematically controlling the electrode potential, we simplified the reaction paths, excluding other unfavorable effects, and thereby obtained only the methanol dehydrogenation activity in terms of the electronic structure of the Pt surface. We observed that the methanol dehydrogenation activity of Pt decreases when the position of the d-band center relative to the Fermi level is lower, and this fundamental relation provides advanced insight into the design of an optimal catalyst as the anode for direct methanol fuel cells

Ultrathin Zirconium Disulfide Nanodiscs

We present a colloidal route for the synthesis of ultrathin ZrS2 (UT-ZrS2) nanodiscs that are ∼1.6 nm thick and consist of approximately two unit cells of S–Zr–S. The lateral size of the discs can be tuned to 20, 35, or 60 nm while their thickness is kept constant. Under the appropriate conditions, these individual discs can self-assemble into face-to-face-stacked structures containing multiple discs. Because the S–Zr–S layers within individual discs are held together by weak van der Waals interactions, each UT-ZrS2 disc provides spaces that can serve as host sites for intercalation. When we tested UT-ZrS2 discs as anodic materials for Li+ intercalation, they showed excellent nanoscale size effects, enhancing the discharge capacity by 230% and greatly improving the stability in comparison with bulk ZrS2. The nanoscale size effect was especially prominent for their performance in fast charging/discharging cycles, where an 88% average recovery of reversible capacity was observed for UT-ZrS2 discs with a lateral diameter of 20 nm. The nanoscale thickness and lateral size of UT-ZrS2 discs are critical for fast and reliable intercalation cycling because those dimensions both increase the surface area and provide open edges that enhance the diffusion kinetics for guest molecules